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| |  DG DISPATCH - RSNA: Glioma or Abscess? Can Quantitative Magnetic Resonance Tell? By W. A. Thomasson, PhD Special to DG News
CHICAGO, IL -- November 29, 2000 -- Quantitative evaluation of magnetic resonance images (MRI) during perfusion makes it possible to distinguish two cerebral lesions - high-grade gliomas and cerebral abscesses - that often produce very similar rim-enhanced MRIs but require quite different treatment. This was the conclusion presented yesterday (Nov. 28) at the annual meeting of the Radiological Society of North America by James M. Provenzale, MD, of Duke University Medical Center, Durham, North Carolina. The technique entails, for each lesion, identifying the enhanced rim and then selecting 30 pixels within the area surrounded by this rim but outside the central, non-perfused region. The cerebral blood volume (CBV) is then calculated for each pixel and the average compared to the average of the corresponding 30 pixels in the contralateral hemisphere. in four patients with biopsy-proven high-grade glioma, Dr. Provenzale and his colleagues found that the ratio of CBV in the lesion to that in normal white matter was consistently above 1.0 (range 1.03 to 2.20). In three patients with cerebral abscesses, the ratio was consistently below 1.0 (range 0.61 to 0.95). A Nocardia abscess was confirmed by biopsy in one patient, while the other two were presumed to have Staphylococcus and Streptococcus abscesses, respectively, on the basis of appropriate responses to therapy. Dr. Provenzale noted that three of the four glioma patients had been previously treated. However, he said, treatment typically reduces rather than increases CBV, so this point is more likely to blunt rather than enhance the distinction from cerebral abscess. This was a small study, he said, and further investigation will be required to determine whether the distinction can be consistently drawn in every case of a larger series, as it was here. Nevertheless, this technique appears to point the way toward an effective non-invasive method for distinguishing between these two types of lesions.
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